Higher recycling at lower temperatures


Dutch construction firm Heijmans has been using a Shell process to make asphalt at lower temperatures than conventional asphalt – using less energy and reducing CO2


emissions.


Heijmans and Shell have now patented a way to incorporate a high percentage of old asphalt. “Our new product contains up to 60% old asphalt, more than the traditional approach,” says Gerbert van Bochove, innovation manager at Heijmans. “And we prepare it about 50ºC cooler than conventional asphalt.” The key to the breakthrough lay


in the composition of a soft type of bitumen that the Shell WAM (warm asphalt mix) process uses to coat the sand and gravel. “The soft bitumen chemically breaks down the recycled asphalt without the need for high temperatures,” says Gerbert. “So it allows us to recycle asphalt at lower temperatures.” To give the resulting road the


necessary performance qualities, a harder bitumen is also added to the asphalt mixture during its preparation. The harder bitumen mixes in easily at the lower temperature, because it is frothed up (foamed) with water before it is added. Heijmans worked with Shell


for around a year to adjust the bitumen ingredients to make the Shell WAM foam process work with recycled asphalt. The final product, Greenway LE


asphalt, was recently laid on a test road along a railway line. Heijmans has now brought the product to the Dutch market, and Shell hopes to license the manufacturing process in other countries in the future.


8


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12